Heat sink

ABSTRACT

A heat sink includes a pillar member, to which a device that generates heat is to be mounted, and a plurality of heat-dissipating fins arranged on a side surface of the pillar member to dissipate the heat generated by the device. The heat sink further includes a ring-shaped holding member that has a plurality of grooves formed therein. The holding member is mounted to a longitudinal end of the pillar member and has each of the heat-dissipating fins inserted in a corresponding one of the grooves of the holding member, thereby holding the heat-dissipating fins to the pillar member. Each of the heat-dissipating fins has a detachment prevention portion that prevents the heat-dissipating fin from being detached from the pillar member in a direction perpendicular to the longitudinal direction of the pillar member.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims priority from Japanese Patent Application No. 2010-206793, filed on Sep. 15, 2010, the content of which is hereby incorporated by reference in its entirety into this application.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates generally to heat sinks which have heat-dissipating fins for dissipating heat generated by devices. More particularly, the invention relates to heat sinks which dissipate heat generated by devices that have high heat-generating density and are remarkably lowered in both performance and service life at high temperature; those devices include, for example, LEDs (Light Emitting Diodes).

2. Description of the Related Art

Japanese Patent No. 4015146 discloses a heat sink that includes a columnar base, to which a heat-generating device is mounted, and a plurality of heat-dissipating fins provided on a radially-outer periphery of the base.

Specifically, in the heat sink, the base has a plurality of grooves formed in a side surface thereof. Each of the heat-dissipating fins is inserted in a corresponding one of the grooves of the base and joined to the base by caulking, more specifically, by plastically deforming those portions of the base which surround the corresponding groove using a pressing jig.

With the above configuration, however, it is necessary to form the grooves in the side surface of the base, thus complicating the manufacture of the heat sink.

Moreover, when the spaces between the heat-dissipating fins are small and/or the outer diameter of the base is small, it may be difficult to insert the pressing jig sufficiently into the spaces between the heat-dissipating fins. Consequently, it may become difficult to reliably perform the caulking process for the heat-dissipating fins.

Furthermore, the stress state around those of the heat-dissipating fins which have been already joined to the base may be influenced by the caulking process for a later one of the heat-dissipating fins. As a consequence, the heat conductivity between those heat-dissipating fins and the base may be lowered.

In addition, when the shape of the heat-dissipating fins and/or the spaces between the heat-dissipating fins are changed with a change in the design specification, it may be necessary to accordingly change the pressing jig for performing the caulking process.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a first heat sink which includes a pillar member, to which a device that generates heat is to be mounted, and a plurality of heat-dissipating fins arranged on a side surface of the pillar member to dissipate the heat generated by the device. The first heat sink further includes a ring-shaped holding member that has a plurality of grooves formed therein. The holding member is mounted to a longitudinal end of the pillar member and has each of the heat-dissipating fins inserted in a corresponding one of the grooves of the holding member, thereby holding the heat-dissipating fins to the pillar member. Each of the heat-dissipating fins has a detachment prevention portion that prevents the heat-dissipating fin from being detached from the pillar member in a direction perpendicular to the longitudinal direction of the pillar member.

According to the present invention, there is also provided a second heat sink which includes a pillar member, to which a device that generates heat is to be mounted, and a plurality of heat-dissipating fins arranged on a side surface of the pillar member to dissipate the heat generated by the device. The second heat sink further includes a plate-shaped holding member that has an insertion hole formed at the center thereof and a plurality of grooves formed to extend from the insertion hole outward. A longitudinal end portion of the pillar member is inserted in the insertion hole of the holding member. The holding member has each of the heat-dissipating fins inserted in a corresponding one of the grooves of the holding member, thereby holding the heat-dissipating fins to the pillar member. Each of the heat-dissipating fins has a detachment prevention portion that prevents the heat-dissipating fin from being detached from the pillar member in a direction perpendicular to the longitudinal direction of the pillar member.

According to the present invention, there is also provided a third heat sink which includes a pillar member, to which a device that generates heat is to be mounted, and a plurality of heat-dissipating fins arranged on a side surface of the pillar member to dissipate the heat generated by the device. The third heat sink further includes a pair of plate-shaped holding members and a plurality of bar members. The holding members are respectively provided at opposite longitudinal ends of the pillar member. Each of the bar members extends in the longitudinal direction of the pillar member with its longitudinal ends respectively engaging with the holding members. Each of the heat-dissipating fins is bent, on the pillar member side and along the longitudinal direction of the pillar member, to form a detachment prevention portion thereof. For each of the heat-dissipating fins, the detachment prevention portion of the heat-dissipating fin is sandwiched between the side surface of the pillar member and a corresponding one of the bar members, thereby preventing the heat-dissipating fin from being detached from the pillar member in a direction perpendicular to the longitudinal direction of the pillar member.

According to the present invention, there is also provided a fourth heat sink which includes a pillar member, to which a device that generates heat is to be mounted, and a plurality of heat-dissipating fins arranged on a side surface of the pillar member to dissipate the heat generated by the device. Each of the heat-dissipating fins is bent, on the pillar member side and along the longitudinal direction of the pillar member, twice to form an overlapping portion and a detachment prevention portion thereof. The overlapping portion extends along the side surface of the pillar member and has a hole formed therein. The detachment prevention portion is formed at a distal end of the overlapping portion so as to protrude from the detachment prevention portion in a direction away from the pillar member. For each adjacent pair of the heat-dissipating fins, the overlapping portions of the pair of the heat-dissipating fins partially overlap each other and the detachment prevention portion of one of the pair of the heat-dissipating fins is inserted in the hole of the other heat-dissipating fin, thereby preventing the heat-dissipating fins from being detached from the pillar member.

With the above configurations of the first to the fourth heat sinks, it is possible to first temporarily assemble the heat-dissipating fins to the pillar member and then joining (e.g., brazing) the heat-dissipating fins to the pillar member in the temporarily-assembled state. As a result, it is possible to make the heat sinks without employing any additional pressing or fixing devices, thus facilitating the manufacture of the heat sinks.

Moreover, with the above configurations, it is not necessary to form grooves in the pillar member. Consequently, it is possible to easily form the pillar member and improve the flexibility in arranging the heat-dissipating fins on the side surface of the pillar member. In addition, it is also possible to improve the flexibility in changing the shape of the heat sinks and to enhance both the strength and heat conductivity of the heat sinks.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detailed description given hereinafter and from the accompanying drawings of preferred embodiments of the invention, which, however, should not be taken to limit the invention to the specific embodiments but are for the purpose of explanation and understanding only.

In the accompanying drawings:

FIG. 1 is an exploded, perspective view illustrating the configuration of a heat sink according to a first embodiment of the invention;

FIG. 2 is a perspective view of the heat sink according to the first embodiment;

FIG. 3 is a cross-sectional view of the heat sink according to the first embodiment;

FIG. 4 is a top view of the heat sink according to the first embodiment;

FIGS. 5A-5D are schematic views illustrating a method of making an annular holding member of the heat sink according to the first embodiment;

FIGS. 6A-6D are perspective views illustrating modifications of the annular holding member;

FIG. 7 is a cross-sectional view illustrating a modification of the heat sink according to the first embodiment;

FIG. 8 is a cross-sectional view illustrating another modification of the heat sink according to the first embodiment;

FIG. 9 is a top view illustrating yet another modification of the heat sink according to the first embodiment;

FIG. 10 is a top view illustrating still another modification of the heat sink according to the first embodiment;

FIG. 11 is an exploded, perspective view illustrating the configuration of a heat sink according to a second embodiment of the invention;

FIG. 12 is a cross-sectional view of the heat sink according to the second embodiment;

FIG. 13 is a cross-sectional view illustrating a modification of the heat sink according to the second embodiment;

FIG. 14 is a cross-sectional view illustrating another modification of the heat sink according to the second embodiment;

FIG. 15 is an exploded, perspective view illustrating the configuration of a heat sink according to a third embodiment of the invention;

FIG. 16 is a perspective view of the heat sink according to the third embodiment;

FIG. 17 is a cross-sectional view of the heat sink according to the third embodiment;

FIG. 18 is an exploded, perspective view illustrating a modification of the heat sink according to the third embodiment;

FIG. 19 is a perspective view illustrating the same modification as illustrated in FIG. 18;

FIG. 20 is an exploded, perspective view illustrating another modification of the heat sink according to the third embodiment;

FIG. 21 is a perspective view illustrating the same modification as illustrated in FIG. 20;

FIG. 22 is an exploded, perspective view illustrating the configuration of a heat sink according to a fourth embodiment of the invention;

FIG. 23 is a perspective view of the heat sink according to the fourth embodiment;

FIG. 24 is an exploded, perspective view illustrating the configuration of a heat sink according to a fifth embodiment of the invention;

FIG. 25 is a perspective view of the heat sink according to the fifth embodiment;

FIG. 26 is a cross-sectional view of the heat sink according to the fifth embodiment;

FIG. 27 is a cross-sectional view illustrating a modification of the heat sink according to the fifth embodiment;

FIG. 28 is an exploded, perspective view illustrating the configuration of a heat sink according to a sixth embodiment of the invention;

FIG. 29 is a perspective view of the heat sink according to the sixth embodiment;

FIG. 30 is an exploded, perspective view illustrating a modification of the heat sink according to the sixth embodiment; and

FIG. 31 is a perspective view illustrating the same modification as illustrated in FIG. 30.

DESCRIPTION OF PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described hereinafter with reference to FIGS. 1-31. It should be noted that for the sake of clarity and understanding, identical components having identical functions in different embodiments of the invention have been marked, where possible, with the same reference numerals in each of the figures and that for the sake of avoiding redundancy, descriptions of the identical components will not be repeated.

First Embodiment

FIGS. 1-4 show the configuration of a heat sink according to a first embodiment of the invention. The heat sink is designed to dissipate heat generated by a device 1 which may be, for example, an LED (Light Emitting Diode) used in a headlamp for a vehicle.

As shown in FIGS. 1-4, the heat sink includes a pillar member 2 and a plurality of heat-dissipating fins 4.

In the present embodiment, the pillar member 2 has a cylindrical shape and is made of, for example, aluminum. The pillar member 2 has an upper end face 2 a on which the device 1 is mounted.

In addition, it should be noted that the pillar member 2 may also have other shapes, for example a tubular shape.

The heat-dissipating fins 4 are provided on the radially outer periphery of the pillar member 2. The heat-dissipating fins 4 are plate-shaped and made of, for example, aluminum. In the present embodiment, the length of the heat dissipating fins 4 in the vertical direction is substantially equal to that of the pillar member 2. In other words, the heat dissipating fins 4 extend over substantially the entire axial length of the pillar member 2.

In addition, it should be noted that the length of the heat dissipating fins 4 may also be set different from that of the pillar member 2.

Each of the heat-dissipating fins 4 is bent, on the pillar member 2 side and along the axial direction (or the longitudinal direction) of the pillar member 2, to form a detachment prevention portion 6. The detachment prevention portion 6 is substantially perpendicular to the rest of the heat-dissipating fin 4.

In the present embodiment, the width of the detachment prevention portions 6 of the heat-dissipating fins 4 is set so that the detachment prevention portions 6 can be arranged on the side surface of the pillar member 2 along the circumferential direction of the pillar member 2 without a gap therebetween. Moreover, the width of the detachment prevention portions 6 is also set so as to be suitable for heat dissipation via air flow through the spaces between adjacent pairs of the heat-dissipating fins 4.

In addition, the detachment prevention portions 6 may be further bent into an arc-shape according to the shape of the side surface of the pillar member 2, so as to make intimate contact with the side surface of the pillar member 2.

The heat sink according to the present embodiment further includes an annular (or circular ring-shaped) holding member 8. The inner diameter of the holding member 8 is set so that when the detachment prevention portions 6 of the heat-dissipating fins 4 are arranged on the side surface of the pillar member 2, the holding member 8 can be mounted on the radially outside of the detachment prevention portions 6. More specifically, in the present embodiment, the inner diameter of the holding member 8 is set to be equal to the sum of the diameter of the pillar member 2 and twice the thickness of the detachment prevention portions 6.

The holding member 8 has a plurality of grooves 10 each of which is formed to extend from the lower end of the holding member 8 upward for a predetermined distance. Moreover, as shown in FIGS. 3 and 4, the holding member 8 is mounted to the upper end of the pillar member 2 so that each of the heat-dissipating fins 4 is inserted in a corresponding one of the grooves 10 of the holding member 8 and the detachment prevention portions 6 are plastically deformed to extend along the side surface of the pillar member 2.

Further, the detachment prevention portions 6 are radially sandwiched between the side surface of the pillar member 2 and the inner surface of the holding member 8, thereby preventing the heat-dissipating fins 4 from being radially detached from the pillar member 2. In other words, each of the heat-dissipating fins 4 is restricted, by the side surface of the pillar member 2 and the inner surface of the holding member 8, from moving in the radial direction of the pillar member 2. Furthermore, each of the heat-dissipating fins 4 is also restricted by the bottom surface of the corresponding groove 10 from moving upward and by the side surfaces of the corresponding groove 10 from moving in the circumferential direction of the pillar member 2.

In the present embodiment, the holding member 8 is made in the following way. First, a drawing process is performed on a circular aluminum plate as shown in FIG. 5A, thereby forming a hat-shaped member as shown in FIG. 5B. Then, a cutting process is performed on the hat-shaped member to remove those unnecessary portions which are shaded in FIG. 5B, thereby obtaining a ring as shown in FIG. 5C. Thereafter, the grooves 10 are formed in the ring, resulting in the annular holding member 8 as shown in FIG. 5D.

FIG. 6A shows a first modification of the holding member 8. In this modification, the holding member 8 is made by: (1) forming the grooves 10 in a flat aluminum band; and (2) rolling the flat aluminum band into a non-closed ring having an opening 8 a.

FIG. 6B shows a second modification of the holding member 8. In this modification, the holding member 8 is made by: (1) forming the grooves 10 in a flat aluminum band; and (2) rolling the flat aluminum band into a closed ring so that longitudinal end portions of the flat aluminum band overlap each other to form an overlapping part 8 b. In addition, during the rolling step, it is preferable to bring the grooves 10 formed in the longitudinal end portions of the flat aluminum band into radial alignment with each other, thereby preventing the holding member 8 from radially expanding.

FIG. 6C shows a third modification of the holding member 8. In this modification, the holding member 8 is made by: (1) forming the grooves 10 in a flat aluminum band; (2) bending longitudinal end portions of the flat aluminum band to the same side, thereby forming butting portions 8 c; and (3) rolling the flat aluminum band into a closed ring so that the butting portions 8 c butt against each other on the radially inside of the ring. In addition, a recess 2 b is formed in the side surface of the pillar member 2 so that the butting portions 8 c of the holding member 8 can be fitted into the recess 2 b, thereby preventing the holding member 8 from radially expanding.

FIG. 6D shows a fourth modification of the holding member 8. In this modification, the holding member 8 is made by: (1) forming the grooves 10 in a flat aluminum band; (2) bending longitudinal end portions of the flat aluminum band to the same side, thereby forming butting portions 8 d; (3) forming a through-hole 8 e in each of the butting portions 8 d; (4) rolling the flat aluminum band into a closed ring so that the butting portions 8 d butt against each other on the radially outside of the ring with the through-holes 8 e in alignment with each other; and (5) passing a blot 12 through the through-holes 8 e and fastening a nut 14 onto the bolt 12, thereby fixing the butting portions 8 d together to prevent the holding member 8 from radially expanding.

Referring back to FIGS. 1-4, the heat sink according to the present embodiment further includes a substantially circular plate-shaped holding member 18. The holding member 18 has an insertion hole 21 and a plurality of grooves 20. The insertion hole 21 is formed at the radial center of the holding member 18 to penetrate the holding member 18 in a thickness-wise direction of the holding member 18′. Each of the grooves 20 is formed in the radially inner surface of the holding member 18 so as to radially extend from the insertion hole 21. Moreover, the grooves 20 are positioned in the circumferential direction of the holding member 18 so that each of the grooves 20 can be aligned with a corresponding one of the grooves 10 of the holding member 8 in the axial direction of the pillar member 2. In addition, in the present embodiment, the depth of the grooves 20 is set to be substantially equal to half the radial width of the holding member 18.

Furthermore, the holding member 18 is bent, at the radially inner end thereof, downward to form guide portions 22. The guide portions 22 together define the insertion hole 21 so that the diameter of the insertion hole 21 is equal to the inner diameter of the holding member 8. The guide portions 22 are separated from one another in the circumferential direction of the holding member 18 by the grooves 20. Moreover, as shown in FIG. 3, the holding member 18 is further bent upward at a radial position corresponding to the bottoms of the grooves 20. Consequently, the grooves 20 are inclined with respect to the axial direction of the pillar member 2 except for those portions of the grooves 20 which are formed between the guide portions 22.

The heat-dissipating fins 4 are arranged on the side surface of the pillar member 2 so as to radially extend from the side surface with the detachment prevention portions 6 in abutment with the side surface. Moreover, lower end portions of the pillar member 2 and the detachment prevention portions 6 are together inserted in the insertion hole 21 of the holding member 18, with each of the heat-dissipating fins 4 partially inserted in a corresponding one of the grooves 20 of the holding member 18. In addition, with the guide portions 22 of the holding member 18, it is possible to easily insert the lower end portions of the pillar member 2 and the detachment prevention portions 6 into the insertion hole 21.

After mounting the holding member 18 to the pillar member 2, the detachment prevention portions 6 of the heat-dissipating fins 4 are sandwiched between the side surface of the pillar member 2 and the inner surfaces of the guide portions 22 of the holding member 18, thereby restricting radial movement of the heat-dissipating fins 4. Moreover, downward movement of the heat-dissipating fins 4 is also restricted by the upper end face of the holding member 18.

Further, with the holding members 8 and 18 mounted to the pillar member 2 and the heat-dissipating fins 4 held by the holding members 8 and 18, the heat-dissipating fins 4 are joined to the pillar member 2 by brazing.

The process of brazing the heat-dissipating fins 4 to the pillar member 2 can be performed using either of the following two methods.

According to the first method, the pillar member 2 includes a brazing filler metal as its clad material. In the brazing process, the temporary assembly of the pillar member 2, the heat-dissipating fins 4 and the holding members 8 and 18 is heated in a furnace, thereby melting the brazing filler metal provided at the surface of the pillar member 2. Consequently, with the molten brazing filter metal, the heat-dissipating fins 4 are brazed to the pillar member 2. Moreover, by capillary action, the molten brazing filler metal flows into the grooves 10 and 20 of the holding members 8 and 18, thereby brazing the heat-dissipating fins 4 to the holding members 8 and 18. As a result, all of the pillar member 2, the heat-dissipating fins 4 and the holding members 8 and 18 are brazed together to make up the heat sink as a good conductor of heat.

On the other hand, according to the second method, the pillar member 2 includes no clad material. Instead, a brazing filler metal in the form of paste is applied to the upper end face 2 a of the pillar member 2. In the brazing process, the temporary assembly of the pillar member 2, the heat-dissipating fins 4 and the holding members 8 and 18 is heated in a furnace, thereby lowering the viscosity of the brazing filler metal. Consequently, the brazing filler metal flows down into all the air gaps between the pillar member 2, the heat-dissipating fins 4 and the holding members 8 and 18, thereby joining them together to make up the heat sink as a good conductor of heat.

After the brazing process, the brazing filler metal which remains on the upper end face 2 a of the pillar member 2 is removed, for example by cutting, thereby making the upper end face 2 a flush with the upper end of the holding member 8. Then, as illustrated in FIG. 2, the device 1 is mounted onto the upper end face 2 a of the pillar member 2.

The heat sink according to the present embodiment has the following advantages.

As described above, in the present embodiment, the heat sink includes the holding members 8 and 18 that hold the heat-dissipating fins 4 to the pillar member 2 (i.e., keep the heat-dissipating fins 4 from moving away from the pillar member 2). Consequently, with the holding members 8 and 18, it is possible to first temporarily assemble the heat-dissipating fins 4 to the pillar member 2 and then perform the process of joining (e.g., brazing in the present embodiment) the heat-dissipating fins 4 to the pillar member 2 in the temporarily-assembled state. As a result, it is possible to make the heat sink without employing any additional pressing or fixing devices, thus facilitating the manufacture of the heat sink. In addition, in operation, the holding members 8 and 18 can also function as heat-dissipating members to dissipate the heat generated by the device 1.

Furthermore, according to the present embodiment, it is not necessary to form grooves in the pillar member 2. Consequently, it is possible to easily form the pillar member 2 and improve the flexibility in arranging the heat-dissipating fins 4 on the side surface of the pillar member 2. Moreover, it is also possible to improve the flexibility in changing the shape of the heat sink and to enhance both the strength and heat conductivity of the heat sink.

It should be noted that though the heat sink according to the present embodiment includes both the annular holding member 8 and the circular plate-shaped holding member 18, it may also be modified to include only one of the holding members 8 and 18.

Moreover, as shown in FIG. 7, the heat sink may also be modified to include two annular holding members 8 that are respectively mounted to the longitudinal ends (i.e., the upper and lower ends) of the pillar member 2.

Alternatively, as shown in FIG. 8, the heat sink may also be modified to include two circular plate-shaped holding members 18 that are respectively mounted to opposite longitudinal end portions (i.e., an upper end portion and a lower end portion) of the pillar member 2.

In the present embodiment, the heat-dissipating fins 4 are continuously arranged over the entire outer circumference of the pillar member 2 (or within the full angular range of 360°). However, as shown in FIG. 9, it is possible to cut off part of the holding member 18 and arrange the heat-dissipating fins 4 only within part of the outer circumference of the pillar member 2 (or within an angular range less than 360°).

In the present embodiment, each of the grooves 20 of the holding member 18 has the corresponding heat-dissipating fin 4 inserted therein. However, as shown in FIGS. 9 and 10, it is also possible for some of the grooves 20 of the holding member 18 not to have the heat-dissipating fins 4 inserted therein.

Further, though not shown in FIGS. 9 and 10, it is also possible to cut off part of the pillar member 2, on which no heat-dissipating fin 4 is arranged, thereby making part of the side surface of the pillar member 2 flat. In this case, the device 1 may be mounted on the flat part of the side surface of the pillar member 2, instead of on the upper end face 2 a of the pillar member 2.

In the present embodiment, the pillar member 2 is configured to have the cylindrical shape. However, it is also possible to configure the pillar member 2 to have a polygonal (e.g., square or hexagonal) prismatic shape and arrange the heat-dissipating fins 4 on the flat side faces of the pillar member 2. In addition, in this case, it is necessary to accordingly modify the holding member 8 to have a polygonal ring shape and the insertion hole 21 of the holding member 18 to be a polygonal hole.

Second Embodiment

FIGS. 11 and 12 show the configuration of a heat sink according to a second embodiment of the invention. The head sink according to the present embodiment is similar to that according to the first embodiment; therefore, only the differences therebetween will be described hereinafter.

In the present embodiment, the heat sink includes a plurality of heat-dissipating fins 24 instead of the heat-dissipating fins 4 in the first embodiment, and a washer member 30 and a bolt 32 instead of the holding member 18 in the first embodiment.

More specifically, in the present embodiment, each of the heat-dissipating fins 24 has a first detachment prevention portion 26 and a second detachment prevention portion 28. The first detachment prevention portion 26 is identical to the detachment prevention portions 6 of the heat-dissipating fins 4 in the first embodiment. The second detachment prevention portion 28 extends radially inward from the lower end of the first detachment prevention portion 26. Further, the second detachment prevention portion 28 tapers radially inward so as to have a trapezoidal shape.

In assembling the heat sink, the heat-dissipating fins 24 are arranged so that the second detachment prevention portions 28 abut the lower end face of the pillar member 2. Then, the washer member 30 is placed to sandwich the second detachment prevention portions 28 of the heat-dissipating fins 24 between the lower end face of the pillar member 2 and the washer member 30. Thereafter, the bolt 32 is passed through a center hole of the washer member 30 and fastened into a threaded hole 33 formed in the lower end face of the pillar member 2. Consequently, the second detachment prevention portions 28 of the heat-dissipating fins 24 are held between the lower end face of the pillar member 2 and the washer member 30, thereby preventing the heat-dissipating fins 24 from being detached from the pillar member 2 in the axial direction (or in the longitudinal direction) of the pillar member 2.

The above-described heat sink according to the present embodiment has the same advantages as that according to the first embodiment.

FIG. 13 shows a modification of the heat sink according to the present embodiment. As shown in the figure, in this modification, a washer member 35 is employed instead of the washer member 30. The washer member 35 has an outer diameter much greater than that of the washer member 30. Consequently, in operation, the washer member 35 can also function as a heat-dissipating member, thereby improving the heat-dissipating capability of the heat sink.

FIG. 14 shows a further modification of the heat sink. As shown in the figure, in this modification, a washer member 37 is employed instead of the washer member 35. The washer member 37 has a circular recess 40 formed in an upper end face 42 thereof. The second detachment prevention portions 28 of the heat-dissipating fins 24 are inserted in the recess 40 of the washer member 37, thereby bringing the upper end face 42 of the washer member 37 into contact with the lower ends of the heat-dissipating fins 24. Further, the upper end face 42 of the washer member 37 is brazed to the lower ends of the heat-dissipating fins 24. Consequently, the heat-dissipating capability of the heat sink is further improved.

Third Embodiment

FIGS. 15-17 show the configuration of a heat sink according to a third embodiment of the invention. The head sink according to the present embodiment is similar to that according to the first embodiment; therefore, only the differences therebetween will be described hereinafter.

In the present embodiment, the heat sink includes a plurality of heat-dissipating fins 34 instead of the heat-dissipating fins 4 in the first embodiment.

More specifically, in the present embodiment, each of the heat-dissipating fins 34 has a detachment prevention portion 36 and a slit 38. The detachment prevention portion 36 is identical to the detachment prevention portions 6 of the heat-dissipating fins 4 in the first embodiment. The slit 38 is formed so as to extend from the upper end of the heat-dissipating fin 34 downward and adjoin the detachment prevention portion 36.

In assembling the heat sink, each of the heat-dissipating fins 34 is inserted in a corresponding one of the grooves 10 of the holding member 8. Consequently, circumferential movement of the heat-dissipating fins 34 is restricted by the holding member 8. Moreover, the holding member 8 is inserted in each of the slits 38 of the heat-dissipating fins 34. Consequently, radial movement of the heat-dissipating fins 34 is also restricted by the holding member 8.

In addition, as in the first embodiment, the detachment prevention portions 36 of the heat-dissipating fins 34 are radially sandwiched between the side surface of the pillar member 2 and the inner surface of the holding member 8. Consequently, radial movement of the heat-dissipating fins 34 is also restricted by the side surface of the pillar member 2 and the inner surface of the holding member 8. Further, each of the heat-dissipating fins 4 is also restricted by the bottom surface of the corresponding groove 10 from moving upward.

Accordingly, with the configuration of the heat-dissipating fins 34 according to the present embodiment, it is possible to more reliably hold the heat-dissipating fins 34 to the pillar member 2.

Moreover, in the present embodiment, the depth of the slits 38 of the heat-dissipating fins 34 is so set that the upper end of the holding member 8 is flush with the upper end face 2 a of the pillar member 2. Consequently, it becomes easier to mount the device 1 on the upper end face 2 a of the pillar member 2.

In addition, the heat sink according to the present embodiment also has the same advantages as that according to the first embodiment.

FIGS. 18 and 19 show a modification of the heat sink according to the present embodiment. As show in the figure, in this modification, the heat-dissipating fins 34 are arranged within only part of the outer circumference of the pillar member 2 (or within an angular range less than 360°). Moreover, a holding member 58 is employed instead of the holding member 18. The holding member 58 has the shape of an incomplete-circular plate so as to occupy the same angular range as the heat-dissipating fins 34. Further, the holding member 58 has a pair of fin portions 60 that are respectively formed at the circumferential ends of the holding member 58 so as to extend upward from the respective circumferential ends. Each of the fin portions 60 has a slit 62 that is formed to extend from the upper end of the fin portion 60 downward so as to allow the holding member 8 to be inserted therein.

FIGS. 20 and 21 show another modification of the heat sink according to the present embodiment. As show in the figure, in this modification, the holding member 18 is omitted from the heat sink. Instead, the holding member 8 is elongated to have the same length in the axial direction of the pillar member 2 as the heat-dissipating fins 34. Further, the depth of the grooves 10 of the holding member 8 is also increased with the axial length of the holding member 8. Consequently, it becomes possible to hold the heat-dissipating fins 34 to the pillar member 2 only by means of the holding member 8 without employing the holding member 18. As a result, it becomes possible to reduce the parts count of the heat sink.

Fourth Embodiment

FIGS. 22 and 23 show the configuration of a heat sink according to a fourth embodiment of the invention. The head sink according to the present embodiment is similar to that according to the first embodiment; therefore, only the differences therebetween will be described hereinafter.

In the present embodiment, the heat sink includes: a plurality of heat-dissipating fins 64 instead of the heat-dissipating fins 4 in the first embodiment; an annular holding member 68 instead of the holding member 8 in the first embodiment; and a circular plate-shaped holding member 78 instead of the holding member 18 in the first embodiment.

More specifically, in the present embodiment, each of the heat-dissipating fins 64 is flat plate-shaped and has a slit 65, a first detachment prevention portion 66, a step 70 and a second detachment prevention portion 72. The slit 35 is formed so as to extend from the upper end of the heat-dissipating fin 64 downward. The first detachment prevention portion 66 adjoins the slit 65 from the radially inner side (i.e., from the pillar member 2 side). The step 70 is formed in the lower end of the heat-dissipating fin 64, resulting in the second detachment prevention portion 72 that protrudes downward.

Similar to the holding member 8 in the first embodiment, the holding member 68 in the present embodiment also has a plurality of grooves 10 formed therein. However, the outer and inner diameters of the holding member 68 are set greater than those of the holding member 8, thereby allowing the holding member 68 to be inserted in each of the slits 65 of the heat-dissipating fins 64 and each of the heat-dissipating fins 64 to be inserted in a corresponding one of the grooves 10 of the holding member 68.

Consequently, in the heat sink according to the present embodiment, the first detachment prevention portions 66 of the heat-dissipating fins 64 are radially sandwiched between the side surface of the pillar member 2 and the inner surface of the annular holding member 68, thereby preventing the heat-dissipating fins 64 from being radially detached from the pillar member 2. In other words, each of the heat-dissipating fins 64 is restricted, by the side surface of the pillar member 2 and the inner surface of the holding member 68, from moving in the radial direction of the pillar member 2. Furthermore, each of the heat-dissipating fins 64 is also restricted by the bottom surface of the corresponding groove 10 from moving upward and by the side surfaces of the corresponding groove 10 from moving in the circumferential direction of the pillar member 2.

Similar to the holding member 18 in the first embodiment, the holding member 78 in the present embodiment also has a plurality of grooves 10 and a plurality of guide portions 22. However, unlike the holding member 18, the holding member 78 is made flat and thus the grooves 20 of the holding member 20 are not inclined with respect to the axial direction of the pillar member 2.

Each of the second detachment prevention portions 72 of the heat-dissipating fins 64 is inserted in a corresponding one of the grooves 20 of the holding member 78, thereby being radially sandwiched between the side surface of the pillar member 2 and the bottom surface of the corresponding groove 20 of the holding member 78. Consequently, each of the heat-dissipating fins 64 is restricted, by the side surface of the pillar member 2 and the bottom surface of the corresponding groove 20, from moving in the radial direction of the pillar member 2. Furthermore, each of the heat-dissipating fins 64 is also restricted by the upper end face of the holding member 78 from moving downward and by the side surfaces of the corresponding groove 20 from moving in the circumferential direction of the pillar member 2.

The above-described heat sink according to the present embodiment has the same advantages as that according to the first embodiment.

Fifth Embodiment

FIGS. 24-26 show the configuration of a heat sink according to a fifth embodiment of the invention. As shown in the figures, the heat sink includes a cylindrical pillar member 2, a plurality of heat-dissipating fins 84, a pair of circular plate-shaped holding members 88, and a plurality of bar members 91.

Each of the heat-dissipating fins 84 is bent, on the pillar member 2 side and along the axial direction (or the longitudinal direction) of the pillar member 2, twice at right angles to form a detachment prevention portion 86. The detachment prevention portion 86 has a groove formed therein; the groove extends in the axial direction of the pillar member 2.

In the present embodiment, the width of the detachment prevention portions 86 of the heat-dissipating fins 84 is set so that the detachment prevention portions 86 can be arranged on the side surface of the pillar member 2 along the circumferential direction of the pillar member 2 without a gap therebetween. Moreover, the width of the detachment prevention portions 86 is also set so as to be suitable for heat dissipation via air flow through the spaces between adjacent pairs of the heat-dissipating fins 84.

Each of the circular plate-shaped holding members 88 has a plurality of circular recesses 90 formed in an end face thereof facing the pillar member 2. The recesses 90 are arranged within an annular area on the end face; the annular area has a radial width substantially equal to the depth of the grooves formed in the detachment prevention portions 86 of the heat-dissipating fins 84.

Each of the bar members 91 is round in shape and has a diameter slightly less than the diameter of the circular recesses 90 of the holding members 88. Further, the length of the bar members 91 is substantially equal to the sum of the length of the pillar member 2 and twice the depth of the recesses 90 of the holding members 88.

In assembling the heat sink, the heat-dissipating fins 84 are arranged on the side surface of the pillar member 2 so as to radially extend from the side surface with the detachment prevention portions 86 in abutment with the side surface. Then, each of the bar members 91 is inserted in a corresponding one of the grooves of the detachment prevention portions 86 of the heat-dissipating fins 84, so that the longitudinal ends (i.e., the upper and lower ends) of the bar member 91 respectively protrudes from the longitudinal ends of the corresponding groove. Thereafter, the holding members 88 are respectively placed on the longitudinal end faces of the pillar member 8, with each of the longitudinal ends of the bar members 91 inserted in a corresponding one of the recesses 90 of the holding members 88. Consequently, a temporary assembly of the pillar member 2, the heat-dissipating fins 84, the holding members 88 and the bar members 91 is obtained.

In the temporary assembly, the detachment prevention portions 86 of the heat-dissipating fins 84 are radially sandwiched between the side surface of the pillar member 2 and the corresponding bar members 91, thereby preventing the heat-dissipating fins 84 from being radially detached from the pillar member 2. In other words, each of the heat-dissipating fins 84 is restricted, by the side surface of the pillar member 2 and the corresponding bar member 91, from moving in the radial direction of the pillar member 2. Furthermore, each of the heat-dissipating fins 84 is also restricted by the corresponding bar member 91 from moving in the circumferential direction of the pillar member 2 and by the holding members 88 from moving in the longitudinal direction of the pillar member 2.

The temporary assembly is then treated in the same manner as described in the first embodiment to braze the heat-dissipating fins 84 to the pillar member 2.

The above-described heat sink according to the present embodiment has the same advantages as that according to the first embodiment.

FIG. 27 shows a modification of the heat sink according to the present embodiment. As shown in the figure, in this modification, the circular recesses 90 in one of the holding members 88 are replaced with a plurality of threaded-holes 90 a, and the bar members 91 are configured as bolts and respectively fastened into the threaded-holes 90 a.

Moreover, in the present embodiment, the pillar member 2 is configured to have the cylindrical shape. However, it is also possible to configure the pillar member 2 to have a polygonal (e.g., square or hexagonal) prismatic shape and arrange the heat-dissipating fins 84 on the flat side faces of the pillar member 2. In addition, in this case, it is possible to accordingly modify the holding members 88 to have a polygonal plate shape.

Furthermore, in the present embodiment, the recesses 90 of the holding members 88 are configured as circular recesses and the bar members 91 are configured as round bars. However, it is also possible to configure the recesses 90 of the holding members 88 as polygonal recesses and to accordingly configure the bar members 91 as polygonal bars.

Sixth Embodiment

FIGS. 28 and 29 show the configuration of a heat sink according to a sixth embodiment of the invention. As shown in the figures, the heat sink includes a cylindrical pillar member 2 and a plurality of heat-dissipating fins 94, but no holding members as in the previous embodiments.

Each of the heat-dissipating fins 94 is bent, on the pillar member 2 side and along the axial direction (or the longitudinal direction) of the pillar member 2, twice at right angles to form an overlapping portion 95 and a detachment prevention portion 96.

In the present embodiment, the width of the overlapping portions 95 of the heat-dissipating fins 94 is set so that the overlapping portions 95 can be arranged, on the side surface of the pillar member 2 and along the circumferential direction of the pillar member 2, to partially overlap one another without a gap therebetween.

For each of the heat-dissipating fins 94, the detachment prevention portion 96 is formed at the circumferentially-distal end of the overlapping portion 95 so as to protrude from the overlapping portion 95 in the radially outward direction (or in the radial direction away from the pillar member 2). Moreover, the detachment prevention portion 96 extends within only part of the length of the overlapping portion 95 in the axial direction of the pillar member 2. On the other hand, the overlapping portion 95 has a rectangular hole 98 that is so formed that the detachment prevention portion 96 of another heat-dissipating fin 94 can be inserted in the rectangular hole 98.

In assembling the heat sink, a first one of the heat-dissipating fins 94 is arranged on the side surface of the pillar member 2 so as to radially extend from the side surface with the overlapping portion 95 thereof in abutment with the side surface. Then, a second one of the heat-dissipating fins 94 is arranged on the side surface of the pillar member 2 so as to radially extend from the side surface with the overlapping portions 95 of the first and second heat-dissipating fins 94 overlapping each other and the detachment prevention portion 96 of the first heat-dissipating fin 94 inserted in the rectangular hole 98 of the second heat-dissipating fin 94. Thereafter, a third one of the heat-dissipating fins 94 is arranged on the side surface of the pillar member 2 so as to radially extend from the side surface with the overlapping portions 95 of the second and third heat-dissipating fins 94 overlapping each other and the detachment prevention portion 96 of the second heat-dissipating fin 94 inserted in the rectangular hole 98 of the third heat-dissipating fin 94. The above process is repeated for the rest of the heat-dissipating fins 94. Finally, the detachment prevention portion 96 of a last one of the heat-dissipating fins 94 is inserted in the rectangular hole 98 of the first heat-dissipating fin 94. As a result, a temporary assembly of the pillar member 2 and the heat-dissipating fins 94 is obtained.

In the temporary assembly, for each adjacent pair of the heat-dissipating fins 94, the overlapping portions 95 of the pair of the heat-dissipating fins 94 partially overlap each other and the detachment prevention portion 96 of one of the pair of the heat-dissipating fins 94 is inserted in the rectangular hole 98 of the other heat-dissipating fin 94. As a result, the heat-dissipating fins 94 are prevented from being detached from the pillar member 2 in either of the radial, circumferential and axial directions of the pillar member 2. In other words, all of the radial, circumferential and axial movements of the heat-dissipating fins 94 are restricted.

The temporary assembly is then treated in the same manner as described in the first embodiment to braze the heat-dissipating fins 94 to the pillar member 2.

The above-described heat sink according to the present embodiment has the same advantages as that according to the first embodiment.

FIGS. 30 and 31 show a modification of the heat sink according to the present embodiment. As shown in the figure, in this modification, the heat-dissipating fins 94 are arranged within only part of the outer circumference of the pillar member 2 (or within an angular range less than 360°). Moreover, an arc-shaped holding member 100 is arranged to cover that part of the outer circumference of the pillar member 2 in which no heat-dissipating fin 94 is arranged. The holding member 100 has both a rectangular hole 102 and a detachment prevention portion 104 formed therein. The rectangular hole 102 is formed close to one circumferential end of the holding member 100 and identical to the rectangular holes 98 of the heat-dissipating fins 94. In the rectangular hole 102, there is inserted the detachment prevention portion 96 of that one of the heat-dissipating fins 94 which adjoins the holding member 100 from the one circumferential end of the holding member 100. The detachment prevention portion 104 is formed at the other circumferential end of the holding member 100 and identical to the detachment prevention portions 96 of the heat-dissipating fins 94. The detachment prevention portion 104 is inserted in the rectangular hole 98 of that one of the heat-dissipating fins 94 which adjoins the holding member 100 from the other circumferential end of the holding member 100.

Moreover, in the present embodiment, the pillar member 2 is configured to have the cylindrical shape. However, it is also possible to configure the pillar member 2 to have a polygonal (e.g., square or hexagonal) prismatic shape and arrange the heat-dissipating fins 94 on the flat side faces of the pillar member 2. Furthermore, in this case, when a holding member 100 is employed as in the above-described modification, it is possible to accordingly modify the holding member 100 to have a flat shape.

While the above particular embodiments and modifications have been shown and described, it will be understood by those skilled in the art that various further modifications, changes, and improvements may be made without departing from the spirit of the invention. 

What is claimed is:
 1. A heat sink comprising: a pillar member to which a device that generates heat is to be mounted; and a plurality of heat-dissipating fins arranged on a side surface of the pillar member to dissipate the heat generated by the device, wherein the heat sink further comprises a ring-shaped holding member that has a plurality of grooves formed therein, the holding member is mounted to a longitudinal end of the pillar member and has each of the heat-dissipating fins inserted in a corresponding one of the grooves of the holding member, thereby holding the heat-dissipating fins to the pillar member, and each of the heat-dissipating fins has a detachment prevention portion that prevents the heat-dissipating fin from being detached from the pillar member in a direction perpendicular to the longitudinal direction of the pillar member.
 2. The heat sink as set forth in claim 1, wherein the heat-dissipating fins are joined to the pillar member by brazing.
 3. The heat sink as set forth in claim 1, wherein for each of the heat-dissipating fins, the detachment prevention portion is formed by bending the heat-dissipating fin on the pillar member side and along the longitudinal direction of the pillar member, and the detachment prevention portion is sandwiched between the side surface of the pillar member and an inner surface of the ring-shaped holding member.
 4. The heat sink as set forth in claim 1, wherein each of the heat-dissipating fins has a slit that is formed to extend from a longitudinal end of the heat-dissipating fin in the longitudinal direction of the pillar member, the holding member is inserted in each of the slits of the heat-dissipating fins, for each of heat-dissipating fins, the detachment prevention portion is made up of a portion of the heat-dissipating fin which adjoins the slit from the pillar member side, and the detachment prevention portion is sandwiched between the side surface of the pillar member and an inner surface of the ring-shaped holding member.
 5. The heat sink as set forth in claim 1, wherein the ring-shaped holding member is a first holding member, and the longitudinal end of the pillar member is a first longitudinal end of the pillar member, the heat sink further comprises a second ring-shaped holding member that has a plurality of grooves formed therein, the second holding member is mounted to a second longitudinal end of the pillar member which is opposite to the first longitudinal end in the longitudinal direction of the pillar member, and the second holding member has each of the heat-dissipating fins inserted in a corresponding one of the grooves of the second holding member, thereby holding the heat-dissipating fins to the pillar member.
 6. A heat sink comprising: a pillar member to which a device that generates heat is to be mounted; and a plurality of heat-dissipating fins arranged on a side surface of the pillar member to dissipate the heat generated by the device, wherein the heat sink further comprises a plate-shaped holding member that has an insertion hole formed at the center thereof and a plurality of grooves formed to extend from the insertion hole outward, a longitudinal end portion of the pillar member is inserted in the insertion hole of the holding member, the holding member has each of the heat-dissipating fins inserted in a corresponding one of the grooves of the holding member, thereby holding the heat-dissipating fins to the pillar member, and each of the heat-dissipating fins has a detachment prevention portion that prevents the heat-dissipating fin from being detached from the pillar member in a direction perpendicular to the longitudinal direction of the pillar member.
 7. The heat sink as set forth in claim 6, wherein the heat-dissipating fins are joined to the pillar member by brazing.
 8. The heat sink as set forth in claim 6, wherein the holding member is bent on the insertion hole side so that the grooves of the holding member are inclined with respect to the longitudinal direction of the pillar member, thereby allowing the heat-dissipating fins to be respectively inserted into the grooves.
 9. The heat sink as set forth in claim 6, wherein for each of the heat-dissipating fins, the detachment prevention portion is formed by bending the heat-dissipating fin on the pillar member side and along the longitudinal direction of the pillar member, and the detachment prevention portion is sandwiched between the side surface of the pillar member and an inner surface of the holding member which defines the insertion hole.
 10. The heat sink as set forth in claim 6, wherein each of the heat-dissipating fins is stepped at a longitudinal end thereof to form the detachment prevention portion that protrudes in the longitudinal direction of the pillar member, and the detachment prevention portion is inserted in the corresponding groove of the holding member.
 11. The heat sink as set forth in claim 6, wherein the plate-shaped holding member is a first holding member, and the longitudinal end portion of the pillar member is a first longitudinal end portion of the pillar member, the heat sink further comprises a second plate-shaped holding member that has an insertion hole formed at the center thereof and a plurality of grooves formed to extend from the insertion hole outward, a second longitudinal end portion of the pillar member, which is opposite to the first longitudinal end portion in the longitudinal direction of the pillar member, is inserted in the insertion hole of the second holding member, and the second holding member has each of the heat-dissipating fins inserted in a corresponding one of the grooves of the second holding member, thereby holding the heat-dissipating fins to the pillar member.
 12. The heat sink as set forth in claim 6, wherein the heat sink further comprises a ring-shaped holding member that has a plurality of grooves formed therein, the ring-shaped holding member is mounted to a longitudinal end of the pillar member, the longitudinal end being opposite, in the longitudinal direction of the pillar member, to the longitudinal end portion of the pillar member which is inserted in the insertion hole of the plate-shaped holding member, and the ring-shaped holding member has each of the heat-dissipating fins inserted in a corresponding one of the grooves of the ring-shaped holding member, thereby holding the heat-dissipating fins to the pillar member,
 13. A heat sink comprising: a pillar member to which a device that generates heat is to be mounted; and a plurality of heat-dissipating fins arranged on a side surface of the pillar member to dissipate the heat generated by the device, wherein the heat sink further comprises a pair of plate-shaped holding members and a plurality of bar members, the holding members are respectively provided at opposite longitudinal ends of the pillar member, each of the bar members extends in the longitudinal direction of the pillar member with its longitudinal ends respectively engaging with the holding members, each of the heat-dissipating fins is bent, on the pillar member side and along the longitudinal direction of the pillar member, to form a detachment prevention portion thereof, for each of the heat-dissipating fins, the detachment prevention portion of the heat-dissipating fin is sandwiched between the side surface of the pillar member and a corresponding one of the bar members, thereby preventing the heat-dissipating fin from being detached from the pillar member in a direction perpendicular to the longitudinal direction of the pillar member.
 14. The heat sink as set forth in claim 13, wherein the heat-dissipating fins are joined to the pillar member by brazing.
 15. The heat sink as set forth in claim 13, wherein each of the holding members has a plurality of recesses formed in an end face thereof facing the pillar member, for each of the bar members, the longitudinal ends of the bar member are respectively inserted in a corresponding pair of the recesses of the holding members, thereby respectively engaging with the holding members, and for each of the heat-dissipating fins, the detachment prevention portion of the heat-dissipating fin has formed therein a groove which extends in the longitudinal direction of the pillar member and in which the corresponding bar member is inserted.
 16. A heat sink comprising: a pillar member to which a device that generates heat is to be mounted; and a plurality of heat-dissipating fins arranged on a side surface of the pillar member to dissipate the heat generated by the device, wherein each of the heat-dissipating fins is bent, on the pillar member side and along the longitudinal direction of the pillar member, twice to form an overlapping portion and a detachment prevention portion thereof, the overlapping portion extending along the side surface of the pillar member and having a hole formed therein, the detachment prevention portion being formed at a distal end of the overlapping portion so as to protrude from the detachment prevention portion in a direction away from the pillar member, and for each adjacent pair of the heat-dissipating fins, the overlapping portions of the pair of the heat-dissipating fins partially overlap each other and the detachment prevention portion of one of the pair of the heat-dissipating fins is inserted in the hole of the other heat-dissipating fin, thereby preventing the heat-dissipating fins from being detached from the pillar member.
 17. The heat sink as set forth in claim 16, wherein the heat-dissipating fins are joined to the pillar member by brazing.
 18. The heat sink as set forth in claim 16, wherein the heat-dissipating fins are arranged within only part of the outer circumference of the pillar member, the heat sink further comprises a holding member that is arranged to cover that part of the outer circumference of the pillar member in which no heat-dissipating fin is arranged, the holding member has a hole formed close to one circumferential end of the holding member and a detachment prevention portion formed at the other circumferential end of the holding member, in the hole of the holding member, there is inserted the detachment prevention portion of that one of the heat-dissipating fins which adjoins the holding member from the one circumferential end of the holding member, and the detachment prevention portion of the holding member is inserted in the hole of that one of the heat-dissipating fins which adjoins the holding member from the other circumferential end of the holding member. 